In "It Can't Happen Here," Sinclair Lewis explores the concept of what constitutes a classic through one character's humorous definition. This character suggests that a classic is simply a book that has gained recognition or notoriety before someone's thirtieth birthday. This perspective emphasizes personal familiarity and societal influence in the recognition of literary works.

This definition invites readers to consider how classics are often shaped by cultural moments and the impact they have on individuals. It reflects the idea that the significance of literature can be linked to personal experience and societal trends rather than strictly literary merit.